Electronics assembly

ABSTRACT

An electronics assembly comprises a frame ( 1 ) that contains a motherboard ( 8 ) and a plurality of daughterboards ( 10 ). The frame has an opening opposite the motherboard to allow insertion of the daughterboards into the frame or removal of the daughterboards from the frame. The frame also has an injector/ejector mechanism ( 16, 18 ) for each daughterboard that is located on the daughterboard or the frame and a flange ( 28 ) that extends adjacent to the opening and on which the injector/ejector mechanism of each daughterboard is attached or engages at different locations along the length thereof. The flange ( 28 ) is divided into separate sections ( 30 ) that correspond to the different locations to allow the flange to flex at any adjacent location during insertion of a daughterboard without the flexing affecting the position of any adjacent location of the flange with respect to the motherboard.

BACKGROUND OF THE INVENTION

The present invention relates to electronics assemblies, and isprimarily concerned with racked assemblies. Many such assemblies will belocated in racks for housing in for example nineteen inch cabinets, orother size cabinets such as twenty three inch or metric cabinets. Theassemblies may for instance be employed as servers for a number ofsystems, for example in local area networks (LANs), wide area networks(WANS), telecommunications systems or other operations such as databasemanagement or as internet servers.

Such an assembly will typically comprise a supporting frame that housesa motherboard or backplane and a number of daughterboards or modulecards that extend in planes generally perpendicular to the plane of themotherboard and which are connected to the motherboard by connectors,e.g. high density connectors, so that the daughterboards can simply beintroduced into the frame through an opening therein opposite themotherboard, located on guides and pushed toward the motherboard inorder to connect them to it.

Each daughterboard usually requires multiple electrical connectionswhich are generally provided by two-part multi-pin electricalconnectors, one part of which is located at the rear of thedaughterboard and the other part provided on the motherboard.

In order to engage the daughterboard and the motherboard connectorsproperly during insertion, and to aid removal of the daughterboards, itis common to employ injector/ejector mechanisms. An injector/ejectormechanism is operated by a user and is intended to ensure an appropriateeven force to be applied to the electrical connectors between themotherboard and the daughterboards during insertion of thedaughterboard, to lock the daughterboard in place during operation ofthe system and to aid disconnection of the electrical connectors duringremoval of the daughterboard. The most common form of injector/ejectormechanism comprises a lever arm that can be pivotally located on aflange on the frame at or adjacent to the opening or, more usually,located on the daughterboard and engage the flange, in order to providea mechanical advantage during connection or disconnection.

One problem that has been encountered with such assemblies, however, isensuring correct electrical connection between the daughterboards andthe motherboard due to dimensional tolerances in the daughterboards andother parts of the assembly. The daughterboards may, for example, havetypical dimensions in the region of 500 mm in the insertion and removaldirection whereas the connectors may have a length of travel betweeninitial contact of the pins and complete mating of the connectors, orso-called “wipe”, as low as 0.5 to 0.8 mm, with the result that becauseof tolerances in the length of the daughterboards, some connectors maybe overstressed while other connectors may not form a good connection.This problem is particularly severe if daughterboards toward the end ofan array are relatively long and cause the flange to bow, whiledaughterboards at the centre of the array are relatively short.

This problem may be resolved by providing a flexible coupling in theinjector/ejector mechanism to allow relative movement of a daughterboardaway from the motherboard while applying a biasing force toward themotherboard. Although such a system is perfectly adequate in resolvingthe problem, it requires discrete components to be incorporated in eachinjector/ejector mechanism and is therefore relatively expensive toimplement.

SUMMARY OF THE INVENTION

According to one aspect, the present invention provides an electronicsassembly which comprises a frame that contains a motherboard and aplurality of daughterboards that extend in a plane generallyperpendicular to the plane of the motherboard and are connected to themotherboard by means of connectors, the frame having:

(i) an opening opposite the motherboard to allow insertion of thedaughterboards into the frame or removal of the daughterboards from theframe in a direction normal to the plane of the motherboard;

(ii) an injector/ejector mechanism for each daughterboard that islocated on the daughterboard or the frame and engages the frame or thedaughterboard respectively in a region adjacent to the opening; and

(iii) a flange that extends therealong at or adjacent to the opening andon which the injector/ejector mechanism of each daughterboard isattached or engages at different locations along the length thereof,

wherein the flange is divided into separate sections that correspond tothe different locations to allow the flange to flex at any locationtherealong during insertion of a daughterboard without the flexingaffecting the position of any adjacent location of the flange withrespect to the motherboard.

According to another aspect, the present invention provides a frame foran electronics assembly which comprises a location in which a planarmotherboard can be received and a plurality of guides that extend in adirection generally normal to the plane of the motherboard when it isreceived in the frame in order to enable a plurality of daughterboardsto be located in the frame in engagement with the motherboard, the framehaving:

(i) an opening opposite the location for the motherboard to allowinsertion of the daughterboards into the frame or removal of thedaughterboards from the frame; and

(ii) a flange that extends therealong at or adjacent to the opening andalong which an injector/ejector mechanism for each daughterboard isattached or can engage at different locations along the length thereof;

wherein the flange is divided into separate sections that correspond tothe different locations to allow the flange to flex at any locationtherealong during insertion of a daughterboard without the flexingaffecting the position of any adjacent location of the flange withrespect to the location of the motherboard.

The assembly and frame according to the invention enable daughterboardsof different dimensional tolerances to be accommodated within the frameand biased into engagement with the motherboard in a particularlyinexpensive manner since no discrete biasing components are required.

The injector/ejector mechanism for each daughterboard may, for example,comprise a lever arm that is located on the daughterboard and engagesthe flange or is located on the flange and engages the daughterboard.Usually the injector/ejector mechanism will be in the form of a leverarm that is pivotally attached to the daughterboard and has a relativelyshort (i.e. in relation to the arm) projection that engages the flangeand moves the daughterboard toward the motherboard when the lever arm ismoved toward the front edge of the daughterboard so that it provides adegree of mechanical advantage during insertion of the daughterboard.

Although only one injector/ejector mechanism has been referred to inrespect of each daughterboard, the assembly will usually have two suchmechanisms for each daughterboard, one mechanism being located at eachend of the front edge of the daughterboard or on each side of theopening and the frame will accordingly have a flange on each side of theopening.

The frame will normally have a strengthening member that extends along aside thereof, and usually along both sides thereof, in the region of theopening in order to provide the frame with rigidity in the plane of thedaughterboards. That is to say, the or each strengthening member willextend along the or each side of the opening in a direction normal tothe plane of the daughterboards in order to reduce the degree to whichthe or each side of the strengthening member bows out in a direction inthe plane of the daughterboards. Typically the strengthening member willextend parallel to and adjacent to the flange. It may be formedseparately from the flange, for example where the flange is formed byfolding a front edge portion of the material forming the sides of theframe, and attached to the sides of the frame in any appropriate manner.Alternatively, if the strengthening member and the flange are in closeproximity to one another, it may be convenient to form them both fromthe same element. For example, they may both be formed together as abeam having a substantially “C” or “S”-shaped cross-section where oneside web of the beam constitutes the flange and a web forming the otherside of the beam constitutes the strengthening member.

Such a form of beam is novel per se and so, according to another aspect,the invention comprises an abutment beam for engaging a plurality ofinjector levers for urging daughterboards onto final engagement with amotherboard in an electronic circuit housed in a casing, the abutmentbeam having a first web attachable to the housing and a second webcomprising a plurality of separated locations for engaging the injectorlevers, each location of the second web being independently flexiblerelative to the first web.

Whether the flange and the strengthening member are formed as separateparts or are formed together, the strengthening member is advantageouslyarranged on the side of the flange between the flange and themotherboard. Such an arrangement enables the injector/ejector mechanism,for example the projection of the lever arm, to bear on the flange whenthe daughterboard is inserted into the frame and the connectors of thedaughterboard and the motherboard are mated, and also when thedaughterboards are retained in position in engagement with themotherboard during operation. In this way, resilient deformation of theseparate sections of the flange will exert a bias force on thedaughterboards to maintain the connectors in engagement whileaccommodating any difference in dimensions of the daughterboards. On theother hand, no such resilient deformation is required when thedaughterboards are removed and so the injector/ejector mechanism canbear on the strength member.

The flange may be divided into the separate sections by formingdiscontinuities such as slots or slits therein at the appropriatepositions, for example by sawing or shearing. There is a relativelylarge degree of freedom in the depth of the slots, although to increasethe distance over which the different sections of the flange may move,the depth of the slots may be as great as the flange width so that a “C”section beam would be cut into a corner of its cross-section. Indeed,the slot depth may be greater where the beam is attached to a side wallof the frame since the wall itself will provide rigidity in thedirection of insertion or removal of the daughterboards. There is,however, not usually any advantage in increasing the depth of the slotsor slits beyond the width of the flange, and where no side wall ispresent the strength of any strengthening member in the direction ofinsertion or removal will be reduced.

Other forms of assembly and frame may be employed within the scope ofthe invention. More than one flange and/or strengthening member may bearranged on each side of the opening, for example, or the flange and/orthe strengthening member may be formed separately as beams having an“L”-shaped cross-section. In addition, instead of a lever arm having asingle projection that bears on different surfaces (the flange and thestrengthening member) for insertion and removal of the daughterboards,two projections may be provided on the lever arm that bear on oppositesides of the flange so that one projection is employed for insertion andthe other is employed for removal.

It is not necessary for the flange and/or the strengthening member to beformed from the same material as each other or as the side wall of theframe but may be formed, for example, from plastics material therebyallowing a different degree of flexibility or rigidity.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described in detailwith reference to the accompanying drawings, in which correspondingparts are given like reference numbers. In the drawings:

FIG. 1 is a side view of a daughterboard in a conventional electronicsassembly;

FIG. 2 is a view taken along the planes of the daughterboards of theassembly of FIG. 1;

FIG. 3 is a top plan view of an electronics assembly according to oneembodiment of the present invention;

FIG. 4 is an enlarged view of a lever arm of the assembly shown in FIG.3;

FIG. 5 is a view of part of the assembly of FIG. 3 taken along theplanes of the daughterboards;

FIG. 6 is an isometric view of part of another embodiment of the presentinvention;

FIG. 7 is an isometric view of a modification of the embodiment shown inFIG. 6; and

FIG. 8 is a section through part of another embodiment of the presentinvention.

DESCRIPTION OF PARTICULAR EMBODIMENTS

Referring now to the drawings, in which like reference numerals are usedto designate corresponding elements, FIG. 1 shows part of a conventionalelectronics assembly in which a frame 1 forming part of the chassis ofthe assembly has two side walls 2 and 4 and a rear wall 6 that houses apcb forming a backplane or motherboard 8. Opposite the motherboard 8 isan opening through which a daughterboard 10 can be inserted into theframe or removed therefrom. The daughterboard can be inserted into theframe and slid along guides (not shown) toward the motherboard until amulti-contact connector 12 on the daughterboard mates with acorresponding multi-contact connector 14 on the motherboard.

In order to facilitate mating of the connectors 12 and 14 duringinsertion of the daughterboard, and also disconnection of the connectorsduring removal of the daughterboard, two injector/ejector arrangementsare provided in the form of a lever arm 16 that is located on each sideof the front edge 18 of the daughterboard and pivotal about a pivot axis20 thereon. The lever arm 16 has a short projection 22 which is locatedbetween opposite sides of a beam 24 of substantially “C”-shapedcross-section when the daughterboard is, as shown, fully inserted intoframe and engaged with the motherboard connector 14. The daughterboardcan be moved out of engagement with the motherboard connector 14 bypulling the lever arms in the direction of arrows A which causes theprojection 22 to bear on the inner web or side arm 26 of the beam 24 andeject the daughterboard in the direction of arrows 13. The same actionsin reverse will cause the daughterboard to be received within the frame1 with the connectors 12 and 14 mated, and the projection 22 bearing onthe outer side arm or flange 28 in order to keep the daughterboards inplace.

FIG. 2 is a schematic view of the frame shown in FIG. 1 with threedaughterboards 10 a, 10 b and 10 c in place in which the twodaughterboards 10 a and 10 c toward the edges of the frame arerelatively large due to dimensional tolerances. This can cause the beam24 to bow outwards (the degree of bowing is grossly exaggerated for thesake of clarity) and cause the distance X between the beam and themotherboard to be increased. If the middle daughterboard 10 b is itselfrelatively short this can cause inadequate mating of the connectors 12 band 14 b. In addition, the outer daughterboards are subject to stress.

FIG. 3 shows one form of assembly according to the invention seenthrough the opening for insertion of the daughterboards, while FIG. 4shows the engagement of one of the lever arms in greater detail and FIG.4 is a side view of part of the beam 24 with the daughterboards inplace. Three daughterboards 10 are inserted into their positions in theframe and three slots for the daughterboards are vacant, exposingconnectors 14 on the motherboard.

Instead of having a pair of continuously formed side arms, the innermostside arm 26 of the beam 24 is continuous while the outermost side arm 28that forms the flange against which the projections 22 of the lever arms16 bear during insertion, is divided into separate sections 30 by meansof slots 32 that extend up to the middle portion 34 of the beam. Bydividing this flange into separate sections 30, each section is capableof flexing to a different degree, as shown in FIG. 5, to accommodatedifferences in length of the various daughterboards without affectingthe distance of the adjacent section 30 to the motherboard, so that allthe daughterboards can be accommodated without being overstressed orforming a poor electrical connection to the motherboard. The innermostside arm 26 of the beam 24 is not divided into sections so that it willstill provide strengthening and rigidity for the side wall in the regionof the front opening of the frame. Indeed, if the frame forms a cardcage within a larger chassis, there may not be any side wall of theframe. In addition, the innermost side arm 26 that forms thestrengthening member provides a surface against which the projections 22on the lever arms 16 can bear when the daughterboard is ejected.

The beam may be formed from the same material as that of the frame andmay be spot-welded, riveted or screwed in place, or it may be formedfrom a different material, for example plastics. In addition, thearrangement may be designed so that, even with a daughterboard 10 at theshortest end of the tolerance range, the daughterboard is held with abias against the motherboard connector.

FIG. 6 is an isometric view of part of a side wall of an alternativeform of assembly according to the invention. In this embodiment theflange 28 is formed directly from the sheet that forms the side wall 36of the frame and slots 32 are cut therein as far as the plane of theside wall in order to divide it into sections 30. A separatestrengthening member 26 in the form of a beam of “L”-shapedcross-section is attached to the side wall 36 of the frame. If desired,the strengthening member could be formed in a side wall 36 of the frameby pressing the sheet from which the side wall is formed to form anoutwardly oriented ledge as shown in FIG. 7.

FIG. 8 shows a further form of assembly according to the invention inwhich the flange 28 on which the projection 22 of the lever arm 16 bearsforms part of a beam 24 of substantially “S”-shaped cross-section. Theoutermost part of the beam 24 against which the projections 22 of thelever arms bear during insertion of the daughterboards and duringretention thereof within the frame is divided into sections for eachdaughterboard in the same manner as shown in FIGS. 3 to 6, while theremaining four surfaces 38, 40, 42 and 44 are continuous and providerigidity to the structure. This design of beam will exhibit stiffnessboth in the direction of insertion and removal of the daughterboards(vertically as shown in FIG. 7) and also in the plane of thedaughterboards (horizontally as shown in FIG. 7) and may be employed forexample where the frame forms a card cage within a larger structure andso no side wall of the frame may be present on either or both sidesthereof.

It would be possible, in the arrangement as shown in FIG. 8, for theslots or slits in the beam 24 to extend further and to divide at leastpart of the surface 38 into sections, thereby allowing a greater degreeof flexing of the sections 30 although the overall stiffness of the beamwould be reduced to some extent.

The scope of the present disclosure includes any novel feature orcombination of features disclosed therein either explicitly orimplicitly or any generalisation thereof irrespective of whether or notit relates to the claimed invention or mitigates any or all of theproblems addressed by the present invention. The applicant hereby givesnotice that new claims can be formulated to such features during theprosecution of this application or of any such further applicationderived therefrom. In particular, with reference to the appended claims,features from dependent claims can be combined with those of theindependent claims and features from respective independent claims canbe combined in any appropriate manner and not merely in the specificcombinations enumerated in the claims.

What is claimed is:
 1. An electronics assembly which comprises a framethat contains a motherboard and a plurality of daughterboards thatextend in a plane generally perpendicular to the plane of themotherboard and are connected to the motherboard by means of connectors,the frame having: (i) an opening opposite the motherboard to allowinsertion of the daughterboards into the frame or removal of thedaughterboards from the frame in a direction normal to the plane of themotherboard; (ii) an injector/ejector mechanism for each daughterboardthat is located on the daughterboard or the frame and engages the frameor the daughterboard respectively in a region adjacent to the opening;and (iii) a flange that extends therealong at or adjacent to the openingand on which the injector/ejector mechanism of each daughterboard isattached or engages at different locations along the length thereof,wherein the flange is divided into separate sections that correspond tothe different locations, by slots or slits that extend from an edge ofthe flange to allow each section of the flange to flex during insertionof a daughterboard without the flexing affecting the position of anyadjacent section of the flange with respect to the motherboard andthereby accommodate differences in lengths of the daughterboards.
 2. Anassembly as claimed in claim 1, wherein the injector/ejector mechanismfor the daughterboard comprises a lever arm that is located on thedaughterboard and engages the flange or is located on the flange andengages the daughterboard.
 3. An assembly as claimed in claim 2, whereinthe lever arm is located on the daughterboard and engages the flange. 4.An assembly as claimed in claim 1, wherein the frame has a strengtheningmember extending along a side thereof in the region of the opening inorder to provide the frame with rigidity in the plane of thedaughterboards.
 5. An assembly as claimed in claim 4, wherein thestrengthening member extends in parallel to, and adjacent to, theflange.
 6. An assembly as claimed in claim 4, wherein the strengtheningmember and the flange are formed from the same element.
 7. An assemblyas claimed in claim 6, wherein the strengthening member and the flangeare formed from a beam having a substantially “C” or “S” shapedcross-section.
 8. An assembly as claimed in claim 4, wherein thestrengthening member is arranged on the side of the flange, between theflange and the motherboard.
 9. An assembly as claimed in claim 8,wherein the injector/ejector mechanism bears on the flange when thedaughterboard is inserted into the frame and bears on the strengtheningmember when the daughterboard is removed.
 10. An assembly as claimed inclaim 1, wherein the flange is divided into the separate sections byslots or slits in the flange.